I've been wanting to make the 'nigella version' for a long time but somehow never seemed to get to it. Reading here brought the resolution up to the top of the list again. Sadly, I couldn't get hold of a decent amount of ground almonds for a reasonable price, just the 45-gram baggies in the supermarket that sell at huuuuuuge profits.
So, the flour-version sounded like a nice alternative. A bit scary, using raw clementines, but oh well... I gave it a try and the cake was absolutely wonderful! I made what we call a 'tulband' (high shape with hole in the middle) and poured some clementine icing over. This was the 'dress rehearsal' for my Dearly Beloved's birthday next week. He enjoyed it very much but has requested a dark chocolate granache to be used next time, a request I am quite happy to fulfill.

The remainder of the cake I took to work on tuesday. It was still wonderfully moist, especially considering I made it saturday morning. Thumbs up!

I made a version of this cake yesterday for a passover seder. Since flour is a no-no for Passover, and so is baking powder, I tried another variant: I separated the eggs, beat the whites until stiff, and then folded them into the batter at the end. The cake rose beautifully. My only complaint is that it's not a very attractive cake, but everyone liked it. Another guest made some wonderful vanilla ice cream, which was a great complement.

Carina, you could always just get a bag of blanched almonds (or whole ones if you like the rustic look) and whiz them in a food processor for a bit- not too long though, just until it's ground into a texture kind of like very coarse wholemeal flour.

I made my second one yesterday, with organic oranges this time. Beautiful. My guests loved it and yey, there's some left for my dinnerguest tonight. Served with a simple vanilla icecream.
I'm not sure about the honey-question - maybe we schould just give it a try, or maybe there's a way to find out how much honey equivalents how much sugar?

One concern about the honey idea: the cake is very moist and you might have to tinker with the almond amount to accommodate another moist ingredient.
As far as how much honey, I'd just taste the batter until it tastes right.